1. Field of the Invention
The present invention relates to energy storage devices, and particularly to an adaptive superconductive magnetic energy storage (SMES) control method and system.
2. Description of the Related Art
Because of diminishing oil reserves and environmental concerns, renewable energy research is gaining momentum. Wind energy in itself encompasses various engineering fields and is rapidly developing into a multi-disciplinary area of research and experimentation. In wind generation systems, the variable speed, doubly fed induction generator (DFIG) is preferred over the permanent magnet synchronous generator (PMSG) for its versatility. Background details on the various wind turbine systems may be found in U.S. patent Publication Ser. No. 13/862,327, filed on Apr. 12, 2013, which is incorporated by reference in its entirety herein. The '327 patent application and the present patent application have a common inventor, Abu Hamed Abdur-Rahim.
The control of energy storage devices fed by the aforementioned wind turbines is necessary, since by controlling the energy storage device, power that flows to the grid can be adjusted. The system dynamics relied upon in some installations use a PI (proportional-integral) controller. Many installations use Fuzzy logic to find the energy storage device controller parameters. A self-tuning fuzzy PID (proportional-integral-derivative) controller has been described in the related art. Robust controllers for output power leveling of energy storage systems are also available in the literature. The use of generalized predictive control has also been reported. Moreover, the literature reports a neural network capable of self-tuning for different operating conditions.
An energy storage device gaining increasing popularity is the superconductive magnetic energy storage (SMES) device. The SMES is a device that can deliver both real and reactive power, and hence provides good damping to a PMSG system.
SMES has found widespread application in power systems. However, studies on application of this powerful energy storage device in PMSG wind generator systems are virtually missing. Because of the erratic nature of wind speed variations, this storage device, which can compensate for both real and reactive power, is expected to be a useful control tool.
Wind turbulence and grid faults are the main concerns in a PMSG wind turbine system. Because of them, systems are not able to meet the active and reactive power demand during these faults. Energy storage devices may improve wind system performance by providing active power to the system at the time of contingencies. Variable speed wind generators integrated with an energy storage system are getting attention in recent times.
Thus, an adaptive superconductive magnetic energy storage (SMES) control method and system solving the aforementioned problems is desired.